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Android Application Overview

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DocID025722 Rev 1

Activity screen

Activity can directly managed is own graphic interface by implementing graphical object in a

static way. To provide more flexibility, android propose a dedicated graphic object called

Fragment. Fragment represents a behavior or a portion of graphic user interface in an

activity. Multiple fragments can be combined in a single activity to facilitate reuse, screen

adaption. Fragment is always embedded in an activity and follows the activity lifecycle.

Broadcast receiver

Broadcast receiver is a component in charge to respond to the system-wide broadcast

announcement like a screen turn off message, a low battery message and so on.

Services

Services are application components which perform long-running operation in background

without providing any user interface. Service runs while the application is still alive

independently the user switches to other activity (from the same application) to other

application.

Content providers

Due to security system used by Android system, Content Providers is the component class

in charge to provide mechanisms for defining data security. They are standard interface to

ensure data sharing between components which not run in the same process. Application

can manipulate its own set of data and store it in file system, SQLite data base or external

storage like SD. Other application can access and modify this set of data by querying it

through the content provided implemented by the data owner application.

Content provider is a part of an application and is in charge to centralized data access from

other foreign components. It can also provide its own UI for working with the data it

provides. To get deeper understanding on content provider, reader can refer itself to

literature from web and more specifically on ‘calendar provider’ and ‘contact provider’ from

Android developer web site.

Application Manifest

Associated to every android application, developer must join an xml application descriptor

file call AndroidManifest.xml. This file located in the application root directory gives a Java

package name for the application used as a unique identifier for the application. Manifest file

lists the permission the application requires to do its job and the minimum android API level

the application requires to be fully functional. It also describes components (ie. Services,

activity, broadcast receiver, content provider) belonging to the application. Each component

declaration gets a java class name which implements the component, a set of properties like

a list of intent messages handled by the component.

Structure of the manifest file

Manifest file is a hierarchy file as show in General structure manifest figure where child

hierarchy must be followed. Element at the same level is generally not ordered.

As manifest file is a key file in android application conception it’s recommended the reader

refers to the android manifest documentation.

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